Semiconductor structures are used in storage elements for many products such as MP3 players, digital cameras, computer files, etc. As the application increases, the demand for the semiconductor structures focuses on small size and large memory capacity.
Designers develop a method for improving the densities of the semiconductor structures, using 3D stack semiconductor structures so as to increase a memory capacity and decrease a cost per cell. However, in 3D devices, especially in OP (oxide/polysilicon) stacking semiconductor structures, the word line resistance is the key factor since the word line resistance will impact the operation speed. Therefore, it is important to manufacture semiconductor structures which can effectively reduce the word line resistance.